[ImageMagick] Useful commands to process images

What is ImageMagick

Many people thing that they need closed sources software to process photos, to create GIF animations, color management and transform images by sizing, croping and rotation.

ImageMagick can do more then what we expect. It can also read and write images in a variety of formats (over 200) including PNG, JPEG, GIF, HEIC, TIFF, DPX, EXR, WebP, Postscript, PDF, and SVG.

ImageMagick is free and open source. It’s available in linux, mac and windows using MinGW .

It’s also available in lib format to make iOS, Windows, Linux Apps and as a php extension called “php7.x-imagick” to build server side image processing.

After installing ImageMagick you should have access to all its tools.

Identify

This tool is necessary to extract image information, specially with -verbose param this command will return all the information of the giving image. Here is an example:

identify -verbose beach-beautiful-bridge-449627.jpg
Image: beach-beautiful-bridge-449627.jpg
  Format: JPEG (Joint Photographic Experts Group JFIF format)
  Mime type: image/jpeg
  Class: DirectClass
  Geometry: 4032x3024+0+0
  Resolution: 72x72
  Print size: 56x42
  Units: PixelsPerInch
  Colorspace: sRGB
  Type: TrueColor
  Base type: Undefined
  Endianess: Undefined
  Depth: 8-bit
  Channel depth:
    Red: 8-bit
    Green: 8-bit
    Blue: 8-bit
  Channel statistics:
    Pixels: 12192768
    Red:
      min: 0  (0)
      max: 255 (1)
      mean: 70.7684 (0.277523)
      standard deviation: 67.0167 (0.262811)
      kurtosis: -0.402136
      skewness: 0.753672
      entropy: 0.888948
    Green:
      min: 0  (0)
      max: 255 (1)
      mean: 158.36 (0.62102)
      standard deviation: 58.2885 (0.228582)
      kurtosis: -0.658039
      skewness: -0.602582
      entropy: 0.962202
    Blue:
      min: 0  (0)
      max: 255 (1)
      mean: 209.097 (0.819987)
      standard deviation: 62.8143 (0.246331)
      kurtosis: 0.66187
      skewness: -1.37573
      entropy: 0.767422
  Image statistics:
    Overall:
      min: 0  (0)
      max: 255 (1)
      mean: 146.075 (0.572843)
      standard deviation: 62.7065 (0.245908)
      kurtosis: -1.24161
      skewness: -0.300494
      entropy: 0.872858
  Rendering intent: Perceptual
  Gamma: 0.454545
  Chromaticity:
    red primary: (0.64,0.33)
    green primary: (0.3,0.6)
    blue primary: (0.15,0.06)
    white point: (0.3127,0.329)
  Matte color: grey74
  Background color: white
  Border color: srgb(223,223,223)
  Transparent color: none
  Interlace: None
  Intensity: Undefined
  Compose: Over
  Page geometry: 4032x3024+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: JPEG
  Quality: 73
  Orientation: Undefined
  Properties:
    date:create: 2019-08-30T09:12:12+00:00
    date:modify: 2019-05-03T13:10:37+00:00
    icc:copyright: Copyright (c) 1998 Hewlett-Packard Company
    icc:description: sRGB IEC61966-2.1
    icc:manufacturer: IEC http://www.iec.ch
    icc:model: IEC 61966-2.1 Default RGB colour space - sRGB
    jpeg:colorspace: 2
    jpeg:sampling-factor: 2x2,1x1,1x1
    signature: 567a0413315a5c6d41a4323b956452b234470449c7244448b2362c73411a0b57
  Profiles:
    Profile-icc: 3144 bytes
  Artifacts:
    verbose: true
  Tainted: False
  Filesize: 2.42723MiB
  Number pixels: 12.1928M
  Pixels per second: 57.8762MP
  User time: 0.200u
  Elapsed time: 0:01.210
  Version: ImageMagick 7.0.8-59 Q16 x86_64 2019-08-04 https://imagemagick.org

With this command line, we can extract colors, pixel, copyright and a lot of informations of a given image.

Inline Image resize

This is the most used command on server size when uploading a gallery. Imagine that you copied a RAW images from an SDCard and you want to resize all the images to a specific ratio. you can run this command when you are on the folder:

cd ~/Images mkdir folder magick '\*.jpg[widthxheight]' folder/%03d.jpg

Inline Image Crop

The same as resizing, croping need the X and Y to define witch part will start croping:

magick '\*.jpg' -crop widthxheight+x+y thumbnail%03d.jpg

Other Image processing commands

There are a lot of commands that correct gamma, alpha, filter, blur, … etc of a given image. These commands are available with convert and mogrify tools. There is also -auto-gamma, -auto-level, -auto-threshold that accepts Kapur and OTSU methods. You have to know that you must have a minimum knowledge of image processing fundamentals that help you making a good magick commands and treatments. All these commands are well documented and explained here https://imagemagick.org/script/command-line-options.php.

The name of these commands are the sameof the theory behind so you can learn about it if you want. Don’t forget that ImageMagick is Open Source and FREE so you can find the codes that makes these function available to you.

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